Best way to get to know busy Starbucks barista?

I always go to the Starbucks that is walking distance from my job. There's a barista that works there which I have a pretty big crush on despite not knowing him from atom, since he's only rang me out once. I just feel a strong sexual tension when I'm in his presence. For example, when I was sitting at the counters close enough to observe what the barista's are making one day, he acted a little nervous and was scrambling while making people's drinks. There was also a point in which we held an intense eye contact from afar for about 3 seconds. What I really want to know is how do I get to know somebody who's too busy doing their job to take time and small talk to customers? This Starbucks is almost always busy because of its location. He also seems a little shy or awkward.. unless I'm reading him wrong. Should I ask for his number, or slide him my number? Also, would it be too disgraceful or embarrassing for me to come back if he wound up not being interested like I feel like he is or already has a girlfriend? I feel so conflicted about something as silly as a crush! I'm also a pretty shy person when it comes to getting to know others. Thanks in advance for answers :)